CANNES, France (CNN) --Mobile industry bosses at the 3GSM congress in Cannes are trying to solve technical problems that are plaguing the spread of camera phones.

Despite a massive growth in sales, camera phones are still causing headaches for most European users. A widespread inability to work across networks is one of the major problems according to industry heads, who admit some products may have been rushed onto the market.

"There has been unusually high demand for camera phones and handset makers are trying to put their products out as soon as possible," says Robert Wakeling, director of product strategy at mobile content specialist Magic4. "The fact is if you rush anything there are possibilities mistakes will happen."

All major mobile makers have launched their version of camera phones which can deliver picture and video messages. And despite the problems, 8.4 million such phones were sold worldwide in the fourth quarter of 2002, compared with 5.2 million in the third quarter -- a rise of 62 percent, according to research consultants Strategy Analytics.

It estimates total global sales of about 20 million camera phones to date.

But network operators are still getting to grips with the demand, says Wakeling. "There is a certain amount of interoperability problems from the operators' side because of the time it takes to deploy technology. European operators have only just begun to install multimedia interfaces needed to be able to connect their services."

New technology will always have teething problems, according to Gordon Saussy, CEO of mobile infrastructure firm Megisto, and one of the keynote speakers at the 3GSM World Congress, which continues at the southern French resort until Friday.

"It's no secret that multimedia interoperability is not there yet. Any new technology is complicated because there are many different vendors trying to make it work together.

"However, we should have all the major problems solved by the end of the year."

One senior executive at the 3GSM conference said: "The mobile industry must make phones as easy to use as possible with fewer knobs and buttons. Otherwise they end up shooting themselves in the foot by bringing ill-designed and poorly functioning products to the market that no-one wants."